﻿// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System.Collections;
using System.ComponentModel;
using System.ComponentModel.Design;
using System.Globalization;

namespace System.Windows.Forms.Design;

/// <summary>
///  UI for the MaskTypeEditor (Design time).
/// </summary>
internal class MaskDesignerDialog : Form
{
    private Label _lblHeader;
    private ListView _listViewCannedMasks;
    private CheckBox _checkBoxUseValidatingType;
    private ColumnHeader _maskDescriptionHeader;
    private ColumnHeader _dataFormatHeader;
    private ColumnHeader _validatingTypeHeader;
    private TableLayoutPanel _maskTryItTable;
    private Label _lblMask;
    private TextBox _txtBoxMask;
    private Label _lblTryIt;
    private readonly MaskedTextBox _maskedTextBox;
    private TableLayoutPanel _okCancelTableLayoutPanel;
    private TableLayoutPanel _overarchingTableLayoutPanel;
    private Button _btnOK;
    private Button _btnCancel;
    private ErrorProvider _errorProvider;

    private readonly List<MaskDescriptor> _maskDescriptors = [];
    private MaskDescriptorTemplate _customMaskDescriptor;
    private SortOrder _listViewSortOrder = SortOrder.Ascending;
    private IContainer _components;
    private readonly IHelpService? _helpService;

    /// <summary>
    ///  Constructor receiving a clone of the MaskedTextBox control under design.
    /// </summary>
    public MaskDesignerDialog(MaskedTextBox instance, IHelpService? helpService)
    {
        if (instance is null)
        {
            Debug.Fail("Null masked text box, creating default.");
            _maskedTextBox = new MaskedTextBox();
        }
        else
        {
            _maskedTextBox = MaskedTextBoxDesigner.GetDesignMaskedTextBox(instance);
        }

        _helpService = helpService;

        InitializeComponent();

        // Enable Vista Explorer listview style
        DesignerUtils.ApplyListViewThemeStyles(_listViewCannedMasks);

        // Non-designer-handled stuff.
        SuspendLayout();

        _txtBoxMask.Text = _maskedTextBox.Mask;

        // Add default mask descriptors to the mask description list.
        AddDefaultMaskDescriptors(_maskedTextBox.Culture);

        //
        // maskDescriptionHeader
        //
        _maskDescriptionHeader.Text = SR.MaskDesignerDialogMaskDescription;
        _maskDescriptionHeader.Width = _listViewCannedMasks.Width / 3;
        //
        // dataFormatHeader
        //
        _dataFormatHeader.Text = SR.MaskDesignerDialogDataFormat;
        _dataFormatHeader.Width = _listViewCannedMasks.Width / 3;
        //
        // validatingTypeHeader
        //
        _validatingTypeHeader.Text = SR.MaskDesignerDialogValidatingType;
        _validatingTypeHeader.Width = (_listViewCannedMasks.Width / 3) - SystemInformation.VerticalScrollBarWidth - 4;  // so no h-scrollbar.
        ResumeLayout(false);

        HookEvents();
    }

    private void HookEvents()
    {
        _listViewCannedMasks.SelectedIndexChanged += listViewCannedMasks_SelectedIndexChanged;
        _listViewCannedMasks.ColumnClick += listViewCannedMasks_ColumnClick;
        _listViewCannedMasks.Enter += listViewCannedMasks_Enter;
        _btnOK.Click += btnOK_Click;
        _txtBoxMask.TextChanged += txtBoxMask_TextChanged;
        _txtBoxMask.Validating += txtBoxMask_Validating;
        _maskedTextBox.KeyDown += maskedTextBox_KeyDown;
        _maskedTextBox.MaskInputRejected += maskedTextBox_MaskInputRejected;
        Load += MaskDesignerDialog_Load;
        HelpButtonClicked += MaskDesignerDialog_HelpButtonClicked;
    }

    [MemberNotNull(nameof(_components))]
    [MemberNotNull(nameof(_lblHeader))]
    [MemberNotNull(nameof(_listViewCannedMasks))]
    [MemberNotNull(nameof(_maskDescriptionHeader))]
    [MemberNotNull(nameof(_dataFormatHeader))]
    [MemberNotNull(nameof(_validatingTypeHeader))]
    [MemberNotNull(nameof(_btnOK))]
    [MemberNotNull(nameof(_btnCancel))]
    [MemberNotNull(nameof(_checkBoxUseValidatingType))]
    [MemberNotNull(nameof(_maskTryItTable))]
    [MemberNotNull(nameof(_lblMask))]
    [MemberNotNull(nameof(_txtBoxMask))]
    [MemberNotNull(nameof(_lblTryIt))]
    [MemberNotNull(nameof(_overarchingTableLayoutPanel))]
    [MemberNotNull(nameof(_okCancelTableLayoutPanel))]
    [MemberNotNull(nameof(_errorProvider))]
    private void InitializeComponent()
    {
        _components = new Container();
        ComponentResourceManager resources = new(typeof(MaskDesignerDialog));
        _lblHeader = new Label();
        _listViewCannedMasks = new ListView();
        _maskDescriptionHeader = new ColumnHeader(resources.GetString("listViewCannedMasks.Columns")!);
        _dataFormatHeader = new ColumnHeader(resources.GetString("listViewCannedMasks.Columns1")!);
        _validatingTypeHeader = new ColumnHeader(resources.GetString("listViewCannedMasks.Columns2")!);
        _btnOK = new Button();
        _btnCancel = new Button();
        _checkBoxUseValidatingType = new CheckBox();
        _maskTryItTable = new TableLayoutPanel();
        _lblMask = new Label();
        _txtBoxMask = new TextBox();
        _lblTryIt = new Label();
        _overarchingTableLayoutPanel = new TableLayoutPanel();
        _okCancelTableLayoutPanel = new TableLayoutPanel();
        _errorProvider = new ErrorProvider(_components);
        _maskTryItTable.SuspendLayout();
        _overarchingTableLayoutPanel.SuspendLayout();
        _okCancelTableLayoutPanel.SuspendLayout();
        ((ISupportInitialize)(_errorProvider)).BeginInit();
        SuspendLayout();
        //
        // maskedTextBox
        //
        resources.ApplyResources(_maskedTextBox, "maskedTextBox");
        _maskedTextBox.Margin = new Padding(3, 3, 18, 0);
        _maskedTextBox.Name = "maskedTextBox";
        //
        // lblHeader
        //
        resources.ApplyResources(_lblHeader, "lblHeader");
        _lblHeader.Margin = new Padding(0, 0, 0, 3);
        _lblHeader.Name = "lblHeader";
        //
        // listViewCannedMasks
        //
        resources.ApplyResources(_listViewCannedMasks, "listViewCannedMasks");
        _listViewCannedMasks.Columns.AddRange(
        [
        _maskDescriptionHeader,
        _dataFormatHeader,
        _validatingTypeHeader
        ]);
        _listViewCannedMasks.FullRowSelect = true;
        _listViewCannedMasks.HideSelection = false;
        _listViewCannedMasks.Margin = new Padding(0, 3, 0, 3);
        _listViewCannedMasks.MultiSelect = false;
        _listViewCannedMasks.Name = "listViewCannedMasks";
        _listViewCannedMasks.Sorting = SortOrder.None; // We'll do the sorting ourselves.
        _listViewCannedMasks.View = View.Details;
        //
        // maskDescriptionHeader
        //
        resources.ApplyResources(_maskDescriptionHeader, "maskDescriptionHeader");
        //
        // dataFormatHeader
        //
        resources.ApplyResources(_dataFormatHeader, "dataFormatHeader");
        //
        // validatingTypeHeader
        //
        resources.ApplyResources(_validatingTypeHeader, "validatingTypeHeader");
        //
        // btnOK
        //
        resources.ApplyResources(_btnOK, "btnOK");
        _btnOK.DialogResult = DialogResult.OK;
        _btnOK.Margin = new Padding(0, 0, 3, 0);
        _btnOK.MinimumSize = new Drawing.Size(75, 23);
        _btnOK.Name = "btnOK";
        _btnOK.Padding = new Padding(10, 0, 10, 0);
        //
        // btnCancel
        //
        resources.ApplyResources(_btnCancel, "btnCancel");
        _btnCancel.DialogResult = DialogResult.Cancel;
        _btnCancel.Margin = new Padding(3, 0, 0, 0);
        _btnCancel.MinimumSize = new Drawing.Size(75, 23);
        _btnCancel.Name = "btnCancel";
        _btnCancel.Padding = new Padding(10, 0, 10, 0);
        //
        // checkBoxUseValidatingType
        //
        resources.ApplyResources(_checkBoxUseValidatingType, "checkBoxUseValidatingType");
        _checkBoxUseValidatingType.Checked = true;
        _checkBoxUseValidatingType.CheckState = CheckState.Checked;
        _checkBoxUseValidatingType.Margin = new Padding(0, 0, 0, 3);
        _checkBoxUseValidatingType.Name = "checkBoxUseValidatingType";
        //
        // maskTryItTable
        //
        resources.ApplyResources(_maskTryItTable, "maskTryItTable");
        _maskTryItTable.ColumnStyles.Add(new ColumnStyle());
        _maskTryItTable.ColumnStyles.Add(new ColumnStyle(SizeType.Percent, 100F));
        _maskTryItTable.ColumnStyles.Add(new ColumnStyle());
        _maskTryItTable.Controls.Add(_checkBoxUseValidatingType, 2, 0);
        _maskTryItTable.Controls.Add(_lblMask, 0, 0);
        _maskTryItTable.Controls.Add(_txtBoxMask, 1, 0);
        _maskTryItTable.Controls.Add(_lblTryIt, 0, 1);
        _maskTryItTable.Controls.Add(_maskedTextBox, 1, 1);
        _maskTryItTable.Margin = new Padding(0, 3, 0, 3);
        _maskTryItTable.Name = "maskTryItTable";
        _maskTryItTable.RowStyles.Add(new RowStyle());
        _maskTryItTable.RowStyles.Add(new RowStyle());
        //
        // lblMask
        //
        resources.ApplyResources(_lblMask, "lblMask");
        _lblMask.Margin = new Padding(0, 0, 3, 3);
        _lblMask.Name = "lblMask";
        //
        // txtBoxMask
        //
        resources.ApplyResources(_txtBoxMask, "txtBoxMask");
        _txtBoxMask.Margin = new Padding(3, 0, 18, 3);
        _txtBoxMask.Name = "txtBoxMask";
        //
        // lblTryIt
        //
        resources.ApplyResources(_lblTryIt, "lblTryIt");
        _lblTryIt.Margin = new Padding(0, 3, 3, 0);
        _lblTryIt.Name = "lblTryIt";
        //
        // overarchingTableLayoutPanel
        //
        resources.ApplyResources(_overarchingTableLayoutPanel, "overarchingTableLayoutPanel");
        _overarchingTableLayoutPanel.ColumnStyles.Add(new ColumnStyle(SizeType.Percent, 50F));
        _overarchingTableLayoutPanel.Controls.Add(_maskTryItTable, 0, 3);
        _overarchingTableLayoutPanel.Controls.Add(_okCancelTableLayoutPanel, 0, 4);
        _overarchingTableLayoutPanel.Controls.Add(_lblHeader, 0, 1);
        _overarchingTableLayoutPanel.Controls.Add(_listViewCannedMasks, 0, 2);
        _overarchingTableLayoutPanel.Name = "overarchingTableLayoutPanel";
        _overarchingTableLayoutPanel.RowStyles.Add(new RowStyle());
        _overarchingTableLayoutPanel.RowStyles.Add(new RowStyle());
        _overarchingTableLayoutPanel.RowStyles.Add(new RowStyle(SizeType.Percent, 50F));
        _overarchingTableLayoutPanel.RowStyles.Add(new RowStyle());
        _overarchingTableLayoutPanel.RowStyles.Add(new RowStyle());
        //
        // okCancelTableLayoutPanel
        //
        resources.ApplyResources(_okCancelTableLayoutPanel, "okCancelTableLayoutPanel");
        _okCancelTableLayoutPanel.ColumnStyles.Add(new ColumnStyle(SizeType.Percent, 50F));
        _okCancelTableLayoutPanel.ColumnStyles.Add(new ColumnStyle(SizeType.Percent, 50F));
        _okCancelTableLayoutPanel.Controls.Add(_btnCancel, 1, 0);
        _okCancelTableLayoutPanel.Controls.Add(_btnOK, 0, 0);
        _okCancelTableLayoutPanel.Margin = new Padding(0, 6, 0, 0);
        _okCancelTableLayoutPanel.Name = "okCancelTableLayoutPanel";
        _okCancelTableLayoutPanel.RowStyles.Add(new RowStyle());
        //
        // errorProvider
        //
        _errorProvider.BlinkStyle = ErrorBlinkStyle.NeverBlink;
        _errorProvider.ContainerControl = this;
        //
        // MaskDesignerDialog
        //
        resources.ApplyResources(this, "$this");
        AcceptButton = _btnOK;
        CancelButton = _btnCancel;
        AutoScaleMode = AutoScaleMode.Font;
        Controls.Add(_overarchingTableLayoutPanel);
        FormBorderStyle = FormBorderStyle.FixedDialog;
        HelpButton = true;
        MaximizeBox = false;
        MinimizeBox = false;
        Name = "MaskDesignerDialog";
        ShowInTaskbar = false;
        SizeGripStyle = SizeGripStyle.Hide;
        _maskTryItTable.ResumeLayout(false);
        _maskTryItTable.PerformLayout();
        _overarchingTableLayoutPanel.ResumeLayout(false);
        _overarchingTableLayoutPanel.PerformLayout();
        _okCancelTableLayoutPanel.ResumeLayout(false);
        _okCancelTableLayoutPanel.PerformLayout();
        ((ISupportInitialize)(_errorProvider)).EndInit();
        ResumeLayout(false);
    }

    /// <summary>
    ///  The current text (mask) in the txtBoxMask control.
    /// </summary>
    public string Mask => _maskedTextBox.Mask;

    /// <summary>
    ///  The current text (mask) in the txtBoxMask control.
    /// </summary>
    public Type? ValidatingType { get; private set; }

    /// <summary>
    ///  A collection of MaskDescriptor objects represented in the ListView with the canned mask
    ///  descriptions.
    /// </summary>
    public IEnumerator MaskDescriptors => _maskDescriptors.GetEnumerator();

    /// <summary>
    ///  Adds the default mask descriptors to the mask description list.
    ///  We need to add the default descriptors explicitly because the DiscoverMaskDescriptors method only adds
    ///  public descriptors and these are internal.
    /// </summary>
    [MemberNotNull(nameof(_customMaskDescriptor))]
    private void AddDefaultMaskDescriptors(CultureInfo culture)
    {
        _customMaskDescriptor = new MaskDescriptorTemplate(null, SR.MaskDesignerDialogCustomEntry, null, null, null, true);

        List<MaskDescriptor> maskDescriptors = MaskDescriptorTemplate.GetLocalizedMaskDescriptors(culture);

        // Need to pass false for validateDescriptor param since the custom mask will fail validation
        // because the mask is empty.
        InsertMaskDescriptor(0, _customMaskDescriptor, validateDescriptor: false);

        foreach (MaskDescriptor maskDescriptor in maskDescriptors)
        {
            InsertMaskDescriptor(0, maskDescriptor);
        }
    }

    /// <summary>
    ///  Determines whether the specified MaskDescriptor object is in the MaskDescriptor collection or not.
    /// </summary>
    private bool ContainsMaskDescriptor(MaskDescriptor maskDescriptor)
    {
        Debug.Assert(maskDescriptor is not null, "Null mask descriptor.");
        Debug.Assert(maskDescriptor.Name is not null, "Mask descriptor should either be valid or equal to _customMaskDescriptor");

        string maskDescriptorName = maskDescriptor.Name.Trim();

        foreach (MaskDescriptor descriptor in _maskDescriptors)
        {
            Debug.Assert(descriptor is not null, "Null mask descriptor in the collection.");

            // descriptor.Name is not null because _maskDescriptors can only contain valid mask descriptors or _customMaskDescriptor
            if (maskDescriptor.Equals(descriptor) || maskDescriptorName == descriptor.Name!.Trim())
            {
                return true;
            }
        }

        return false;
    }

    /// <summary>
    ///  Uses the specified ITypeDiscoveryService service provider to discover MaskDescriptor objects from
    ///  the referenced assemblies.
    /// </summary>
    public void DiscoverMaskDescriptors(ITypeDiscoveryService? discoveryService)
    {
        if (discoveryService is null)
        {
            return;
        }

        ICollection descriptors = DesignerUtils.FilterGenericTypes(discoveryService.GetTypes(typeof(MaskDescriptor), false /* excludeGlobalTypes */));

        // Note: This code assumes DesignerUtils.FilterGenericTypes return a valid ICollection (collection of MaskDescriptor types).
        foreach (Type t in descriptors)
        {
            if (t.IsAbstract || !t.IsPublic)
            {
                continue;
            }

            // Since mask descriptors can be provided from external sources, we need to guard against
            // possible exceptions when accessing an external descriptor.
            try
            {
                MaskDescriptor maskDescriptor = (MaskDescriptor)Activator.CreateInstance(t)!;
                InsertMaskDescriptor(0, maskDescriptor);
            }
            catch (Exception ex) when (!ex.IsCriticalException())
            {
            }
        }
    }

    /// <summary>
    ///  Gets the index of a mask descriptor in the mask descriptor table.
    /// </summary>
    private int GetMaskDescriptorIndex(MaskDescriptor maskDescriptor)
    {
        for (int index = 0; index < _maskDescriptors.Count; index++)
        {
            MaskDescriptor descriptor = _maskDescriptors[index];

            if (descriptor == maskDescriptor)
            {
                return index;
            }
        }

        Debug.Fail("Could not find mask descriptor.");
        return -1;
    }

    /// <summary>
    ///  Selects the mask descriptor corresponding to the current MaskedTextBox.Mask if any, otherwise the custom entry.
    /// </summary>
    private void SelectMtbMaskDescriptor()
    {
        int selectedItemIdx = -1;

        if (!string.IsNullOrEmpty(_maskedTextBox.Mask))
        {
            for (int selectedIndex = 0; selectedIndex < _maskDescriptors.Count; selectedIndex++)
            {
                MaskDescriptor descriptor = _maskDescriptors[selectedIndex];

                if (descriptor.Mask == _maskedTextBox.Mask && descriptor.ValidatingType == _maskedTextBox.ValidatingType)
                {
                    selectedItemIdx = selectedIndex;
                    break;
                }
            }
        }

        if (selectedItemIdx == -1) // select custom mask.
        {
            selectedItemIdx = GetMaskDescriptorIndex(_customMaskDescriptor);

            if (selectedItemIdx == -1)
            {
                Debug.Fail("Could not find custom mask descriptor.");
            }
        }

        if (selectedItemIdx != -1)
        {
            SetSelectedMaskDescriptor(selectedItemIdx);
        }
    }

    /// <summary>
    ///  Selects the specified item in the ListView.
    /// </summary>
    private void SetSelectedMaskDescriptor(MaskDescriptor maskDex)
    {
        int maskDexIndex = GetMaskDescriptorIndex(maskDex);
        SetSelectedMaskDescriptor(maskDexIndex);
    }

    private void SetSelectedMaskDescriptor(int maskDexIndex)
    {
        if (maskDexIndex < 0 || _listViewCannedMasks.Items.Count <= maskDexIndex)
        {
            return;
        }

        _listViewCannedMasks.Items[maskDexIndex].Selected = true;
        _listViewCannedMasks.FocusedItem = _listViewCannedMasks.Items[maskDexIndex];
        _listViewCannedMasks.EnsureVisible(maskDexIndex);
    }

    /// <summary>
    ///  Sorts the maskDescriptors and the list view items.
    /// </summary>
    private void UpdateSortedListView(MaskDescriptorComparer.SortType sortType)
    {
        if (!_listViewCannedMasks.IsHandleCreated)
        {
            return;
        }

        MaskDescriptor? selectedMaskDex = null;

        // Save current selected entry to restore it after sorting.
        if (_listViewCannedMasks.SelectedItems.Count > 0)
        {
            int selectedIndex = _listViewCannedMasks.SelectedIndices[0];
            selectedMaskDex = _maskDescriptors[selectedIndex];
        }

        // Custom mask descriptor should always be the last entry - remove it before sorting array.
        _maskDescriptors.RemoveAt(_maskDescriptors.Count - 1);

        // Sort MaskDescriptor collection.
        _maskDescriptors.Sort(new MaskDescriptorComparer(sortType, _listViewSortOrder));

        // Since we need to pre-process each item before inserting it in the ListView, it is better to remove all items
        // from it first and then add the sorted ones back (no replace). Stop redrawing while we change the list.

        PInvokeCore.SendMessage(_listViewCannedMasks, PInvokeCore.WM_SETREDRAW, (WPARAM)(BOOL)false);

        try
        {
            _listViewCannedMasks.Items.Clear();

            string nullEntry = SR.MaskDescriptorValidatingTypeNone;

            foreach (MaskDescriptor maskDescriptor in _maskDescriptors)
            {
                string validatingType = maskDescriptor.ValidatingType is not null ? maskDescriptor.ValidatingType.Name : nullEntry;

                // Make sure the sample displays literals.
                MaskedTextProvider mtp = new(maskDescriptor.Mask!, maskDescriptor.Culture);
                bool success = mtp.Add(maskDescriptor.Sample!);
                Debug.Assert(success, "BadBad: Could not add MaskDescriptor.Sample even it was validated, something is wrong!");
                // Don't include prompt.
                string sample = mtp.ToString(false, true);

                _listViewCannedMasks.Items.Add(new ListViewItem([maskDescriptor.Name!, sample, validatingType]));
            }

            // Add the custom mask descriptor as the last entry.
            _maskDescriptors.Add(_customMaskDescriptor);
            _listViewCannedMasks.Items.Add(new ListViewItem([_customMaskDescriptor.Name, "", nullEntry]));

            if (selectedMaskDex is not null)
            {
                SetSelectedMaskDescriptor(selectedMaskDex);
            }
        }
        finally
        {
            // Resume redraw.
            PInvokeCore.SendMessage(_listViewCannedMasks, PInvokeCore.WM_SETREDRAW, (WPARAM)(BOOL)true);
            _listViewCannedMasks.Invalidate();
        }
    }

    /// <summary>
    ///  Inserts a MaskDescriptor object in the specified position in the internal MaskDescriptor collection.
    /// </summary>
    private void InsertMaskDescriptor(int index, MaskDescriptor maskDescriptor)
    {
        InsertMaskDescriptor(index, maskDescriptor, true);
    }

    private void InsertMaskDescriptor(int index, MaskDescriptor maskDescriptor, bool validateDescriptor)
    {
        if (validateDescriptor && !MaskDescriptor.IsValidMaskDescriptor(maskDescriptor))
        {
            return;
        }

        if (!ContainsMaskDescriptor(maskDescriptor))
        {
            _maskDescriptors.Insert(index, maskDescriptor);
        }
    }

    /// <summary>
    ///  Canned masks list view Column click event handler. Sorts the items.
    /// </summary>
    private void listViewCannedMasks_ColumnClick(object? sender, ColumnClickEventArgs e)
    {
        // Switch sorting order.
        switch (_listViewSortOrder)
        {
            case SortOrder.None:
            case SortOrder.Descending:
                _listViewSortOrder = SortOrder.Ascending;
                break;
            case SortOrder.Ascending:
                _listViewSortOrder = SortOrder.Descending;
                break;
        }

        UpdateSortedListView((MaskDescriptorComparer.SortType)e.Column);
    }

    /// <summary>
    ///  OK button Click event handler. Updates the validating type.
    /// </summary>
    private void btnOK_Click(object? sender, EventArgs e)
    {
        if (_checkBoxUseValidatingType.Checked)
        {
            ValidatingType = _maskedTextBox.ValidatingType;
        }
        else
        {
            ValidatingType = null;
        }
    }

    /// <summary>
    ///  Canned masks list view Enter event handler. Sets focus in the first item if none has it.
    /// </summary>
    private void listViewCannedMasks_Enter(object? sender, EventArgs e)
    {
        if (_listViewCannedMasks.FocusedItem is not null || _listViewCannedMasks.Items.Count <= 0)
        {
            return;
        }

        _listViewCannedMasks.Items[0].Focused = true;
    }

    /// <summary>
    ///  Canned masks list view SelectedIndexChanged event handler. Gets the selected canned mask
    ///  information.
    /// </summary>
    private void listViewCannedMasks_SelectedIndexChanged(object? sender, EventArgs e)
    {
        if (_listViewCannedMasks.SelectedItems.Count == 0)
        {
            return;
        }

        int selectedIndex = _listViewCannedMasks.SelectedIndices[0];
        MaskDescriptor maskDescriptor = _maskDescriptors[selectedIndex];

        // If one of the canned mask descriptors chosen, update test control.
        if (maskDescriptor != _customMaskDescriptor)
        {
            _txtBoxMask.Text = maskDescriptor.Mask;
            _maskedTextBox.Mask = maskDescriptor.Mask;
            _maskedTextBox.ValidatingType = maskDescriptor.ValidatingType;
        }
        else
        {
            _maskedTextBox.ValidatingType = null;
        }
    }

    private void MaskDesignerDialog_Load(object? sender, EventArgs e)
    {
        UpdateSortedListView(MaskDescriptorComparer.SortType.ByName);
        SelectMtbMaskDescriptor();
        _btnCancel.Select();
    }

    private void maskedTextBox_MaskInputRejected(object? sender, MaskInputRejectedEventArgs e)
    {
        _errorProvider.SetError(_maskedTextBox, MaskedTextBoxDesigner.GetMaskInputRejectedErrorMessage(e));
    }

    private static string HelpTopic
    {
        get
        {
            return "net.ComponentModel.MaskPropertyEditor";
        }
    }

    /// <summary>
    ///  Called when the help button is clicked.
    /// </summary>
    private void ShowHelp()
    {
        if (_helpService is not null)
        {
            _helpService.ShowHelpFromKeyword(HelpTopic);
        }
        else
        {
            Debug.Fail("Unable to get IHelpService.");
        }
    }

    private void MaskDesignerDialog_HelpButtonClicked(object? sender, CancelEventArgs e)
    {
        e.Cancel = true;
        ShowHelp();
    }

    private void maskedTextBox_KeyDown(object? sender, KeyEventArgs e)
    {
        _errorProvider.Clear();
    }

    /// <summary>
    ///  Mask text box Leave event handler.
    /// </summary>
    private void txtBoxMask_Validating(object? sender, CancelEventArgs e)
    {
        try
        {
            _maskedTextBox.Mask = _txtBoxMask.Text;
        }
        catch (ArgumentException)
        {
            // The text in the TextBox may contain invalid characters so we just ignore the exception.
        }
    }

    /// <summary>
    ///  Mask text box TextChanged event handler.
    /// </summary>
    private void txtBoxMask_TextChanged(object? sender, EventArgs e)
    {
        // If the change in the text box is performed by the user, we need to select the 'Custom' item in
        // the list view, which is the last item.

        MaskDescriptor? selectedMaskDex = null;

        if (_listViewCannedMasks.SelectedItems.Count != 0)
        {
            int selectedIndex = _listViewCannedMasks.SelectedIndices[0];
            selectedMaskDex = _maskDescriptors[selectedIndex];
        }

        if (selectedMaskDex is null || (selectedMaskDex != _customMaskDescriptor && selectedMaskDex.Mask != _txtBoxMask.Text))
        {
            SetSelectedMaskDescriptor(_customMaskDescriptor);
        }
    }
}
